linux-kernel - Re: [PATCH v4 14/14] of: Improve __of_add_property

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Message-ID: <954725b5-5d53-4bd0-9a06-61ac1aa35dfe@icloud.com>
Date: Mon, 13 Jan 2025 23:00:12 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Rob Herring <robh@...nel.org>
Cc: Saravana Kannan <saravanak@...gle.com>, Maxime Ripard
 <mripard@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Grant Likely <grant.likely@...retlab.ca>, Marc Zyngier <maz@...nel.org>,
 Andreas Herrmann <andreas.herrmann@...xeda.com>,
 Marek Szyprowski <m.szyprowski@...sung.com>,
 Catalin Marinas <catalin.marinas@....com>, Mike Rapoport <rppt@...nel.org>,
 Oreoluwa Babatunde <quic_obabatun@...cinc.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH v4 14/14] of: Improve __of_add_property_sysfs()
 readability

On 2025/1/11 04:41, Rob Herring wrote:
>> From: Zijun Hu <quic_zijuhu@...cinc.com>
>>
>> __of_add_property_sysfs() hard codes string "security-" length as 9, but
>> that is not obvious for readers.
>>
>> Improve its readability by using strlen().
> Does the compiler optimize the strlen call away? Maybe, maybe not. If 
> not, that's N calls to strlen() where N is the number of properties in 
> your DT. That's in the 1000s easily.
> 
> Do you really want to go test enough compiler versions we support to 
> feel confident this is optimized away. I don't.

i understand your concern about performance.

what about below solution ?

 int __of_add_property_sysfs(struct device_node *np, struct property *pp)
 {
+#define SECURITY_PREFIX "security-"
        int rc;

        /* Important: Don't leak passwords */
-       bool secure = strncmp(pp->name, "security-", 9) == 0;
+       bool secure = strncmp(pp->name, SECURITY_PREFIX,
sizeof(SECURITY_PREFIX) - 1) == 0;

        if (!IS_ENABLED(CONFIG_SYSFS))
                return 0;